The catch there is that Allied Races have always been culturally distinct from the “core” race.
Yes, they could have added brown skintones to Orcs, but AU Mag’har are culturally distinct.
Yes, they could have lit a few beards on fire, but Dark Iron Dwarves are culturally distinct.
Yes, they could have just given us antlers, but Highmountain Tauren are culturally distinct.
And so on.
The same would prove true for the vast majority of “subrace”-esque Allied Race suggestions. Wildhammer Dwarves, Dragonmaw Orcs, Grimtotem Tauren, Forest Trolls, Earthen, Arathi Humans, Fel Orcs, Broken Draenei, and such… none of these make complete sense if they’re added under the umbrella of the “core” races.
Even the most popular suggestion of all time, High Elves, are predicated almost entirely on being culturally distinct from Blood and Void Elves.
They’re still relatively low effort additions. I just like seeing those cultural distinctions given a nice coat of paint with a few unique customizations, racials and class options to distinguish them. This wouldn’t be possible if we just amalgamated them all.